1. Field of the Invention
This invention relates to machines of the kind in which an operative member under the actuation of driving means is reciprocatable relative to a guide member in a predetermined direction in order to exert in that direction forces on one or more workpieces, and in which the operative member has such extent in at least one direction in a plane perpendicular to its direction of movement that it is likely to be subjected to tilting loads. If such tilting loads are permitted to cause tilting of the operative member, the machine will not operate properly as intended and may even become damaged.
It is to be understood that the tilting load on the operative member may not only be caused by mistakes made in the operation of the machine but may as well be a forseeable consequence of the kind of work to be carried out by the machine, or of the particular design of the same, such as for example, when the operative member is directly actuated by two or more pressure fluid operated cylinders which need a mechanical intercoupling to cooperate in desired synchronism.
Typical examples of machines of the kind in question are presses, in particular presses used in working sheet metal, such as drawing presses, folding presses, shearing machines and the like. However, also in many other machines, in which the stroke of the operative member is short as compared with the length and/or width of said member measured in a plane perpendicular to the direction of movement thereof, similar problems in preventing the operative member from tilting are encountered.
2. Description of the Prior Art
In conventional machines of the kind referred to hereinbefore the operative member is most commonly designed to move in sliding contact with columns or rails forming part of a machine frame and thus constituting a kind of guide member therein. If in such machines severe tilting problems are anticipated, they are usually met by extending the length, counted in the direction of movement of the operative member, over which guidance is effected. The result of this frequently is that the machine becomes extremely heavy and ungainly.
Through the French Patent Publication No. 2,461,577 there is also known a press of the kind referred to, in which a press platen of rectangular shape and considerable horizontal extent is vertically movable in a frame and is driven by a fairly complex driving arrangement supported by an elongate bridge which is movable relative to the press platen as well as to the frame, and on which mutually parallel driving shafts provided with pinions are journalled in fixed bearings, one at each end of the bridge. By means of a motor supported by the bridge the two driving shafts may be simultaneously rotated in opposite directions in order to cause the bridge to "climb" upwards or downwards relative to the frame, whereby the press platen in its turn will move in the same direction as the bridge but twice as long a distance as the bridge itself. The primary conception behind this arrangement evidently is to uniformly distribute the driving power of the motor to the four corners of the rectangular press platen, whereby a tilting of the press platen is prevented. However, for practical use this known arrangement is scarcely attractive because of its complex design, its consequent sensivity to breakdowns, and the evident difficulties in transmitting to the press platen the great forces, not rarely in the magnitude of 1 MN (meganewton) or more, which are often required for carrying out the pressing operation.